Thermographic diazotype reproduction material, method of making and method of using



Dec. 21, 1965 R. J.

THERMOGRAPHIC DIAZOT MAKING AN Filed INVENTORSIJ ROBERT J. KLIMKOWSKI LU IGI AMARITI ALLAN JAND ATTORNEYS United States Patent THERMOGRAPHEC DIAZGTYPE REPRODUCTION MATERIAL, METHDD OF MAKING AND METH- GD GE USING Robert J. Klirnliowski and Luigi Amariti, Chicago, and Allan D. Jauda, Berwyn, Ill., assignors to Eugene Dietzgen Co., Chicago, 111., a corporation of Delaware Filed Dec. 1, 1961, Ser. No. 156,260 14 Claims. (Cl. 9549) The present invention relates to the production of diazotype photoprinting materials. More particularly, the subject invention is directed to improved diazotype photoprinting compositions which are developed under the influence of heat.

In diazotype photoprinting processes, a suitable base such as paper is treated with a solution of two dye components. One of the components is a diazo compound which is sensitive to light, and the other component is an azo coupling compound. The coupling compound is capable of reacting under proper conditions with the diazo component to form a dye. In making a print, the treated base is exposed to light under a translucent original or master. In those areas of the base which are reached by the light, the diazo compound is at least partially destroyed. In those areas that are beneath opaque lines or designs, on the other hand, the diazo compound is not affected by the light. The print is developed by reacting the retained diazo compound with the coupler to form a highly colored azo dyestulf in precise duplication of the original.

Diazotype reproduction processes are classified as either moist processes or dry processes. In a moist process the base is coated with a diazo compound which is exposed to light under a pattern. Thereafter, color development is brought about by contacting the latent diazo image with a solution of a coupling compound and aqueous alkali. In the dry process the light sensitive layer contains both the diazo compound and a coupler together with acids and various other stabilizing substances. After the treated base has been exposed to light the print is formed by the use of hot aqueous ammonia fumes.

Each of the above systems has serious disadvantages. The principal objection to the dry process is that it requires the use of ammonia fumes. Because of the pungent and corrosive nature of the fumes it is necessary to provide special venting devices before the process can be used to any great extent. Although the moist process does not require the use of ammonia fumes it has the disadvantage that the developing solution must be mixed frequently because it is susceptible to oxidation. Furthermore, the evaporation of water from the developer causes crystallization to occur and often leaves a sticky mass on the developing machine.

Many attempts have been made to provide practical twocomponent thermographic diazotype reproduction materials which can be used in place of systems requiring developing solutions and/ or alkaline vapors. Until very recently, these efforts for the most part were unsuccessful. Difficulties arose because of the dual need to prevent premature reaction between the diazo compound and the coupling component and to cause a rapid reaction between the components at the desired time. In the first heat developable systems, satisfactory shelf life was only accomplished at the expense of print quality. Stabilizing methods such as placing the coupler within a gelatin coating and dusting powdered coupler on the diazo coated paper prevented precoupling but also resulted in the development of faint and weak reproductions.

More recently, a heat developable diazotype system has been developed which is feasible from a commercial standpoint. In this system a layer containing an intimate mixture of a diazo compound, an azo coupling component, and an alkali generating compound is formed on a suitable base. A solution of the various materials is brushed or otherwise applied to the base. Following the removal of volatiles from the liquid coat, the paper, cloth, plastic, etc., is ready for photoprinting. A description of a preferred heat developable process is disclosed in a copending application Serial No. 5,688 which was filed on February 1, 1960. The disclosure of application Serial No. 5,688 is incorporated in the present specification by reference.

Even though the most recent heat developable processes provide commercially acceptable results, there is still room for improvement both as to the shelf life of the coated materials and as to the color density of the resultant reproduction.

It is an object of the present invention to provide improved diazotype photoprinting materials and methods.

Another object of the invention is to provide heat developable diazotype photoprinting materials which have an excellent shelf life.

A further object of the invention is to provide stable diazotype photoprinting materials which produce permanent prints of excellent quality.

Still another object is to provide improved diazotype photoprinting materials which are not subject to the harmful effects of moisture.

A still further object is to provide diazotype photoprinting materials and methods which produce prints having excellent color density.

Other objects will become apparent to those,skilled in the art from the following detailed description of the invention.

In general, the present invention comprises the discovery that the stability of heat developable diazotype photoprinting compositions can be materially improved by incorporating in such compositions a metal sulfate. The sulfate additive can be selected from among the following sulfates: cadium sulfate, zinc sulfate, nickel sulfate, cobalt sulfate, aluminum sulfate, magnesium sulfate, and ceric ammonium sulfate. Our preferred sulfates are cadmium sulfate and zinc sulfate.

Although the actual mechanism by which the metal sulfates improve the shelf life and stability of the heat developable compositions is not fully understood, it is believed that the sulfates complex with urea to form a complex which is stable under normal storage conditions. This complex, however, decomposes at higher temperatures thereby releasing ammoniato catalyze the reaction between the diazo compound and the azo coupling agent. T he complexed urea is less hygroscopic than urea itself which would tend to increase the stability of the system. Furthermore, the formation of the complex would prevent urea from interacting with itself, which interaction produces compounds which do not catalyze the heat development of the azo dye.

In practicing the invention, a suitable base is coated with a mixture of a diazo compound, an azo coupling component, and acid stabilizer, and a metal sulfate of the type described above. Preferably, a solution of the various materials of the system is prepared, which solution is then applied to a suitable base. Thereafter, the volatile constituents of the solution are removed. Prints are produced by exposing the treated base to the action of ultraviolet rays through the master to be copied. The rays destroy or otherwise inactivate the print forming components in all areas of the coated material which are not protected by the lines or designs of the original. The print is formed by heating the exposed base above the temperature required to decompose urea. The ammonia that is generated causes a substantially instant reaction between the coupler and the diazo compound. Alternatively, the print may be made by applying infrared radiation to the original while the original is in contact with the reproduction material. In this manner the design or letter areas of the original are heated above the temperature at which urea decomposes. The heat thus generated is transmitted to the reproduction paper whereupon ammonia producing an alkaline reaction which causes the azo compound intermediates to couple. The resulting print is a precise positive copy of the original.

A thermally developable diazo system is illustrated by the attached schematic drawings in which:

FIG. 1 is an enlarged fragmentary cross-section of a sheet of reproduction material embodying the invention and shown in print making relation to a graphic original to be copied;

FIGS. 2-8 inclusive are sectional views, similar to FIG. 1, showing preferred methods of employing the reproduction material in making copies;

FIG. 9 illustrates in greater detail the reproduction method shown in FIG. 5, which may be referred to as direct printing; and

FIG. illustrates a modified reproduction method, which may be referred to as reflex printing.

The reproduction or copy material 1 illustrated in the drawings is composed of a sensitive layer 2 on a suitable base 3, such as conventional diazo process paper. The layer 2 preferably contains a coupling diazo compound, an azo coupling component, an acid stabilizer, a metal sulfate of the type described, and a compound which produces an alkaline reaction when heated. It is preferred that a diazoniurn salt be employed Which is decomposed or otherwise inactivated or rendered incapable of coupling by exposure to ultraviolet radiations.

As shown in FIGS. 2, 3 and 4 of the drawings, the reproduction material ll may be used to make a print of a graphic original 4- comprising a sheet or base layer 5 of suitable material, such as paper or other graphically markable sheet material, containing a design, drawing, written or type characters, or other graphic representations 6 to be copied, by superimposing the original upon a sheet of the reproduction material 1, to form an exposure sandwich S. Ultraviolet radiations Rv are then applied through the original, as shown in FIG. 2, in order to decompose or otherwise inactive one or both of the diazonium salt and azo coupling component of the sensitive material in all areas 2' thereof except the copy area 6', corresponding with the design 6 to be copied, where the sensi tive layer 2 is screened from impingement of ultraviolet radiation by the ray opaque nature of the design to be copied. As a consequence, the sensitive coating material which remains intact in the areas 6 forms a latent image of the design 6 to be copied, which latent image may be developed or converted to a stable image 6", highly visible by contrast against the background areas 2', merely by heating the sheet above the temperature at which urea decomposes and evolves ammonia in the areas 6. Such development of a stable visible image 6 by the application of heat is shown in FIGS. 3 and 4. Heat for developing the stable image may be applied in any convenient manner, by any suitable or preferred heating means, and may be applied either directly to the copy sheet 2, as shown in FIG. 3, or indirectly thereto, through the master 4, as shown in FIG. 4.

Developing heat may be applied to layer 2 either through body 3 of the reproduction material or through master 4 while the master and reproduction material are in contact. The constituents may be separated after exposure to ultraviolet radiation, however, in order that developing heat may be applied only to the exposed sheet of reproduction material. In such case developing heat may be applied directly to the surface of the sheet which carries heat sensitive layer 2.

The sheet of reproduction material may be applied in sandwhieh S With its face 7 engaging the back or remote face of the master, as shown in FIGS. 1-4, so that the latent image-forming radiation Rv will reach the sensitive layer after passing through the master only. Alternately, the design carrying surface 8 of master 4 can be placed in contact with the back side of the copying sheet, that is to say, the surface of the sheet that is remote from the sensitive layer 2. When so arranged, the radiations Rv should be passed through the master from its design remote side to and through its design carrying surface and thence through the body or base layer 3 of the copying sheet 1. In either case the resulting print comprises the reproduced graphic characters 6", in heat and light stable condition, visible by contrast against the background areas 2', which are also heat and light stable.

Where ultraviolet radiation is employed to stabilize the background areas prior to development, it is possible to make several copies of an original or master simultaneously, by including several sensitive sheets 1 in superimposed stack relation beneath the master 4 in the exposure sandwich. The limiting factor in the simultaneous production of multiple copies, of course, is the intensity of the source of ultraviolet radiation and the ultraviolet transparency of the reproduction material 1.

Reproduction material embodying the present invention may also be used to make copies of graphic material without first inactivating the background areas 2 by exposure to ultraviolet rays. This can be accomplished by exposing the sandwich radiation adapted to be absorbed by the material of the graphic representations 6 to be copied, and to be converted to heat at the locus or =locii of the graphic representations. Visible light, especially in the orange and red spectral zones, as well as invisible infrared radiation is capable of absorption by graphite, carbon and like graphic materials commonly employed in printing, typewriting, drawing and other graphic procedures. As a consequence copies of graphic material 6, as shown in FIG. 5, may be produced by forming a copying sandwich S in which the master 4 and a sheet of reproduction material 1 are juxtaposed in fashion permitting the heat produced at the graphic areas 6 of the master to be applied to the registering areas 6' of the sensitive layer 2. Such areas are thus heat developed and converted to stable condition visible by contrast against the surrounding undeveloped portions or layer 2. To this end, the sandwich S may be exposed to radiation from a source of infrared and/ or visible light rays Re preferably containing orange and red spectral components convertible to heat upon absorption by the material of the graphic contents 6 of the master to be copied. The radiation is either absorbed or reflected by the original 4, according to the degree of absorptivity of the portions of the original upon which the radiation impinges. The absorbed radiant energy is converted to heat which, as shown at H, is transmitted to the adjacent areas of the reproduction material 1; and a permanent color change takes place in the heatsensitive layer 2, producing a developed area 6 duplicating the design 6 on the original.

The foregoing is all that is required to produce a permanent copy in this embodiment of the invention. In particular, when employing a substance such as urea which is inactive at ambient temperatures, as the preferred alkali generator, the background will remain in its original undeveloped condition.

If it is desired to decompose the background diazo compound such as in the case of a colored background which may be rendered colorless, or to render the background incapable of development in response to subsequent application of heat to the print, the developed copy material as shown in FIGS. 68 may be exposed to ultraviolet radiations. Artificial radiations such as are produced by a mercury vapor lamp or natural ultraviolet radiation as is found in sunlight may be employed for this purpose. Exposure to sunlight or another source of ultraviolet radiations improves the contrast and the appearance of the copy by destroying the undeveloped material in the background areas 2. Another important advantage of the present process is that the copy, if desired, can be rendered completely insensitive to heat.

The direct reproduction method illlustrated in FIGS. 5 and 9 is especially suited for producing dense contrasting images employing azo dye intermediates. It is also adapted for destruction of the background diazo compound by exposure to ultraviolet radiations, before, during, or after exposure to heat-producing radiations.

In this method, the original 4 is interposed between the heat-producing radiation source 9 (FIG. 9) and the copy paper 1. The materials are preferably in face-to-back contact, with the respective face surfaces 7 and 8 of the copy paper and the original nearer the radiation source in each case. Either face surface, or both of them, may constitute the side of the material more distant from the radiation source, having regard to the nature of the materials employed and particularly the requirements for transmitting radiant and/ or heat energy. Various different effects can be produced by such variations in the manner of known thermographic materials.

The radiant energy source 9 is preferably arranged with the original and copy materials for scanning the latter. Radiations Re are concentrated and focused on the face surface 8 of the original, in an elongated zone normal to the face of the drawing, while the sandwich moves with respect to said zone in the direction of the arrow, from right to left, viewing FIG. 9. As each portion of the sandwich passes through in the focal zone, radiations are absorbed by the design areas 6 and transformed into heat, which, as shown at H, is conducted, through the base 5 of the original, to the sensitive layer 2 of the copy material. The alkali generator in the sensitive layer produces an alkaline reaction when heated, which raises the pH of the layer sufficiently to cause the diazo compound and coupler therein to couple. The coupling reaction produces a color change, resulting in a permanent positive image 6" on the face surface 7 of the copy paper, which precisely duplicates the design 6 of the original 4.

The radiations which are not absorbed by the design 6 are reflected, as illustrated at 13, or may be transmitted through the base 5 of the original depending upon the material used. The transmitted rays normally do not affect the reproduction if the original bears a design only on the face surface. It has been found that if absorbing materials intervene, as in the case of a base 5 printed on both sides, it is still often possible to focus the radiation source 9 and adjust its output so as to selectively copy the front surface in an acceptable manner. Alternatively, the base material 5 of the original may be appropriately specified.

In an alternative method, the materials may be exposed more widely to radiations of sutficient intensity. Thus, a complete sheet may be copied at one time without moving the materials.

The reflex method illustrated in FIG. 10 is suited to situations where there may be interference with the direct method. For example, the base 5 of the original may be less heat conductive than desirable, or printing on the back surface of the original may cause interference. For this method, the reproduction material 1 may be selected according to known principles for transmission of the radiations Re and conduction of heat energy H.

In the reflex method, the radiations Re pass through the copy material 1 and strike the original. Radiations striking the design 6 are converted to heat which is conducted as indicated at H to the sensitive layer 2 of the copy material. An image 6" is produced, which duplicates the original design 6. Radiations not absorbed are reflected as shown at 13 or transmitted, depending upon the materials.

The materials again are preferably in face-to-back contact, or may be rearranged for different effects employing suitable materials. The background may be decom- 6 posed by exposure to ultraviolet radiations following exposure to the heat-producing radiations.

An additional advantage found in incorporating metal sulfates in the heat developable system lies .in the ability of the sulfates to form complexes with ammonia. If urea is used as the alkali regenerating material and if the urea were to hydrolyze in storage yielding ammonia, the metal sulfate would be able to complex the ammonia so as to prevent a premature reaction. of the diazo compound and coupler. At higher temperatures, however, these complexes apparently are unstable so that they do not interfere with the developing process. A still further advantage to be found in adding metal sulfates such as cadmium sulfate and zinc sulfate to the heat developable diazotype composition lies in the ability of these sulfates to form hydrated salts. A formulation containing such compounds would be protected to a substantial degree from moisture by virtue of the fact that these materials would remove the moisture by the formation of hydrates. In this Way, salts of the diazo and coupler would not hydrolyze and, consequently, good shelf life is maintained.

The diazo compound is present as a diazonium salt at the time it is exposed to the heat source. It is preferred to employ as the diazo compound one of the commonly used stabilized diazonium salts, preferably the zinc chloride double salt. Other stabilized derivatives may be used, for example, the cadmium chloride or stannic chloride double salts, or the fluoborates.

Exemplary diazo compounds which may be employed are the diazonium alts obtained by diazotization of the following amines:

It is preferred to employ a diazonium salt, in the form of a stabilized derivative as indicated above, having the following structural formula:

X represents an acid anion, such as a halide or a sulfate ion, R is hydrogen or an aliphatic radical, preferably alkyl, aralkyl, hydroxyalkyl, or a radical which together with R and N forms a cyclic basic amine radical. R is an aliphatic radical, preferably alkyl, aralkyl, hydroxyalkyl, or a radical which together with R and N forms a radical of a cyclic basic amine. R and R may be hydrogen, alkyl, or alkoxy. The several alkyl radicals are preferably lower alkyl radicals. In addition to these preferred compounds, it is contemplated that other compounds might be employed, such as those having the foregoing composition and which contain an acyl group as R and/or R The following azo coupling agents are among those which can be used in the subject process and in preparing the subject products:

2,3dihydroxynaphthalene 2,3-dihydroxynaphthalene-6-sulfonic acid Resorcinol Acetoacetanilide 7-hydroxy-l,Z-naphthimidazole l-phenyl-3 -methyl--pyrazolone 2-naphthol-3,6-disulfonic acid and the like.

When employing the coupling components having a high coupling energy, such as resorcinol and acetoacetanilide, it is advisable to select a diazo compound having a small coupling energy, and the diazo layer may require a higher degree of stabilization against precoupling.

It is desirable to add an organic acid stabilizing agent to the composition. These agents include such acids as malonic, gluconic, cyanoacetic, maleic, tartaric, citric, diglycolic, oxalic, acetic, and malic acids, and anhydrides of such acids, e.g., the lactones. Reference to such acids is intended to include the equivalent anhydrides. Other acids which have been found to be of substantial help in maintaining the stability of the compositions and improving shelf life are aromatic sulfonic acids such as m-benzenedisulfonic acid. The use of such agents is described in copending application Serial No. 67,289 which was filed on November 4, 1960, now abandoned. The disclosure of said application is incorporated in the present specification by reference.

Preferred compounds which produce an alkaline reaction when heated include those which yield ammonia by decomposition or dissociation. The compounds include, for example, the ureas, i.e., urea and its derivatives, in particular, guanidine, alkyl substituted urea and alkyl substituted guanidines, said alkyl groups containing from 1 to 4 carbon atoms such as methyl urea, ethyl urea, propyl urea, and butyl urea, and hydroxy ureas such as hydroxy methyl urea and hydroxy ethyl urea. It is often advantageous to use a plurality of such compounds, such as mixtures of urea and guanidine, and urea and tetramethyl guanidine. Other compounds of this type which can be used in the subject process include sulfamide and cyanamide.

Organic nitrogen base salts which produce an alkaline reaction when heated may be employed, particularly salts of amines with volatile or decomposable acids such as acetic acid, malonic acid, gluconic acid, and other heat fugitive acids. Amino-parafiins and especially hydroxylated derivatives thereof or amino alcohols are preferred, particularly those having low volatility, substantial alkalinity, and no odor, and which are resistant to oxidation. Examples of such amines are tri-(hydroxymethyl)- aminomethane, 2-amino-2-methyl-l, 3-propanediol, ethanolamine, diethanolamine, and ethyl diethanolamine. The aforementioned guanidines are also basic, and their basicity may provide or contribute to the necessary alkaline reaction, with or without decomposition thereof to produce ammonia. Other compounds which are contemplated include the ammonium salts of weak acids, such as ammonium gluconate, ammonium acetate, ammonium carbonate, ammonium diglycolate, and ammonium oleate. The compounds containing the ammonium ion presently are not preferred as the materials produced therewith tend to have a reduced shelf life.

Paper, cloth, plastic sheet materials, plastic impregnated materials, and metal bodies all may be employed as the base material in the direct printing process, provided that the material is not so heat-conductive as to interfere with the process when employing the method of FIG. 9. The reproduction material for use in the reflex process as illustrated in FIG. requires that the base be capable of transmitting the heat-producing radiations, and conducting the heat from the original to the sensitive layer. Various drafting and printmaking papers are suitable, as are regenerated cellulose, synthetic plastic and other such sheet materials capable of transmitting the radiation without substantial absorption thereof.

The diazo compound, coupling component, acid stabilizer, metal sulfate, and alkali generator are applied to the base in solution by one of the conventional coating methods. The materials are preferably dissolved in water, and the one-phase liquid coat is dried by evaporation to a residual moisture content of preferably less than about 5%. A volatile organic solvent may also be employed, although such is not ordinarily necessary and therefore is not preferred due to the increased cost and normal disadvantages attendant upon such use. It is necessary that the solvent be one which can be removed substantially completely in the drying process, so as not to have an adverse effect on the shelf life.

The diazo compound is preferably employed in a proportion of about 1 to 10% by weight on the basis of the water or other solvent content of the sensitizer composition. The composition is applied to the base at standard rates of application, for example, application to diazo process paper is made at the rate of about 10 to grams of diazo compound per one thousand square feet.

The coupling component is employed in a proportion preferably at least sufiicient to constitute a stoichiometric amount with respect to the diazo compound, and preferably in substantial excess. Thus, about 2 to 15 equivalents of coupler per equivalent of diazo compound is preferred in most cases.

The quantity of alkaline reacting material employed should be sufficient to elevate the pH of the sensitized layer to that required for coupling, and this quantity Will likewise depend upon the characteristics of the material and of the other substances in the sensitive layer. It has been found, for example, that compounds of the type of urea may be employed in a weight ratio to diazo compound of about 325 :1. The proportion of an amino alcohol while varying with its basicity and molecular weight, will frequently be in the range of about 0.510 parts by weight to 1 part of diazo compound. Other compounds may be employed at rates corresponding thereto on the basis of the ammonia evolved or the resulting pH change.

The amount of metal sulfate which is added to the composition will vary in accordance with the amount of urea or other alkali generating agent which is present in the system. It has been found that one mol of the metal surface should be present for each 3 to 20 mols of urea. Our preferred ratio of urea to metal sulfate is from about 5 to 15 mols of urea per mol of metal sulfate, and our most preferred is from about 7 to about 13 mols of urea for each mol of the metal sulfate.

The conditions of time and temperature for developing the image are selected for the system employed to produce the necessary alkaline reaction without undesirable decomposition of the diazo compound. The results are generally advantageous when the sensitive layer is subjected to a relatively high temperature of about C. to 220 C. for a short time, ranging from a few seconds to about a minute. While rapid development is preferred, the materials can be heated for a longer period of time at a lower temperature. As an example, the temperatures reached in the sensitive layers in the examples which follow were about 205 C. to 220 C. for a period of about six to fifteen seconds. These rates are very advantageous and enable a number of copies to be made in a short period of time.

Such temperatures may be provided in the sensitive layer in a number of ways. Thus, the primary source of the necessary heat as illustrated in the drawings at 9 may be a quartz lamp used in conjunction with an elliptical reflector so as to provide an intense zone of near infrared and infrared light. The lamp may produce a color temperature of about 2750 K. with about 9 1500 watts. The reflector ellipse dimensions may be 0.750 inch for the minor axis and 0.845 inch for the major axis. The tungsten element of the lamp is located at one focus of the ellipse, and the surface 8 of the original or master 4 at the other.

The duplicating machine may be allowed to operate without cooling the parts, so that part of the heat increment is supplied by the parts such as the rollers or conveyor means, or the heat produced by absorption of the radiations may be supplemented in another manner. If the background diazo compound is first decomposed in the direct process the latent image produced thereby may be developed if desired by contact with a heated surface.

The following examples are illustrative of the invention. The original and reproduction paper were placed inface-to-back contact in each case and conducted through the focal zone of an infrared beamproduced as described above. The materials travelled through the focal zone at a rate of 1 to 2 inches per second, and reached temperatures of about 205 C. to 220 C. It will be understood that the invention is not limited to the examples, nor to the materials, proportions, and procedures set forth therein.

Example 1 Standard commercial diazo process paper was coated at the rate of about 30 g. of a diazo compound per 1,000 square feet of the composition having the following proportions:

Water ml 100 Urea g 20 Thiourea g 2 m-Benzenedisulfonic acid g 6 Resorcinol g 8 Cadmium sulfate g 12 N-p-diazophenylmorpholine g 7 Saponin g 0.25

The above formulation yielded a sepia line. The shelf life of the paper was found to be excellent. The process illustrated in FIG. 9 of the drawing produced clear and vivid copies of various papers bearing typewritten and printed subject matter from diazo process paper coated with the above composition.

Example I1 Standard commercial diazo process paper was coated in the same manner as described in Example I with each of the following compositions:

Water ml 100 Colloidal silica g 11 Cadmium sulfate g 30 Urea g 50 m-Benzenedisulfonic acid g 8 2,3 dihydroxynaphthalene-6-sulfonic acid sodium salt g 8 p-Diazophenylmorpholine zinc chloride g 2 Silicic acid g Rice starch g 5 Water ml 100 Urea g 50 Zinc sulfate g 15 m-Benzenedisulfonic acid g 8 2,3-dihydroxynaphthalene-6sulfonic acid g 10 p-Diazophenylmorpholine zinc chloride g 4 Saponin g 0.5

Water ml 100 Urea g 50 Cadmium sulfate g 21 m-Benzenedisulfonic acid g 7 2,3-dihydroxynaphthalene-6-sulfonic acid u g 6 p-Diazophenylmorpholine zinc chloride g 3 Silicic acid g 10 Rice starch g 10 10 The above compositions produced a blue line. In each instance, the reproduction material was found to have excellent shelf life and print forming characteristics.

Example Ill Standard commercial diazo process paper was coated in the same manner as described in Example I with each of the following compositions:

Water ml Urea g 55 Cadmium sulfate g 25 Resorcinol g 4 2,3-dihydroxynaphthalene-6-sulfonic acid g 2 m-Benzenedisulfonic acid g 8 p-Diazophenylmorpholine zinc chloride g 3 Silicic acid g 5 Rice starch g 5 Water mL. 100 Urea g 50 Cadmium sulfate g 30 Resorcinol g 4 2,3 dihydroxynaphthalene-6-sulfonic acid sodium salt g 2 m-Benzenedisulfonic acid g 10 p-Diazophenylmorpholine zinc chloride g 4 Silicic acid g 5 Rice starch g 6 Water rnl 100 Urea g 60 m-Benzenedisulfonic acid g 10 Resorcinol g 6 2,3-dihydroxynaphthalene-6-sulfonic acid g 2.6 Zinc sulfate g 10 p-Diazophenylmorpholine zinc chloride g 5 The above compositions produced a black line. In each instance, the reproduction material was found to have excellent shelf life and print forming characteristics.

The use of nickel sulfate, cobalt sulfate, aluminum sulfate, magnesium sulfate, and ceric ammonium sulfate as substitutes for cadmium sulfate and zinc sulfate in the above formulations provide compositions which also have excellent shelf life. The prints that are formed from such compositions are also highly satisfactory even though they are somewhat less dense in color than are those prints produced using formulations containing either cadmium sulfate or zinc sulfate.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as. are indicated in the appended claims.

We claim:

1. Reproduction material which comprises a supported layer of a visibly heat-sensitive composition, said composition comprising a mixture of a coupling diazo compound, an azo coupling component, a complex of cadmium sulfate and a compound producing an alkaline reaction when heated, said compound being selected from the group consisting of urea, guanidine, alkyl substituted ureas, alkyl substituted guanidines, hydroxy methyl urea, and hydroxy ethyl urea, said alkyl groups containing 1 to 4 carbon atoms, the mol ratio of said compound producing an alkaline reaction when heated to said cadmium sulfate being from about 3:1 to about 20:1, and the weight ratio of said compound producing an alkaline reaction when heated to said diazo compound being from 3-25: 1.

2. Reproduction material as in claim 1 wherein said compound producing an alkaline reaction is urea.

3. Reproduction material which comprises a supported layer of a visibly heat-sensitive composition, said composition comprising a mixture of a coupling diazo compound, an azo coupling component, a complex of zinc sulfate and a compound producing an alkaline reaction when heated, said compound being selected from the group consisting of urea, guanidine, alkyl substituted ureas, alkyl substituted guanidines, hydroxy methyl urea, and hydroxy ethyl urea, said alkyl groups containing 1 to 4 carbon atoms, the mol ratio of said compound producing an alkaline reaction when heated to said zinc sulfate being from about 3:1 to about 20:1, and the weight ratio of said compound producing an alkaline reaction when heated to said diazo compound being from 3-25: 1.

4. Reproduction material as in claim 3 wherein said compound producing an alkaline reaction is urea.

5. An improvement in a process for producing reproduction material wherein a base is coated with an aqueous solution of a coupling diazo compound, an azo coupling component, and a compound producing an alkaline reaction when heated, said compound being selected from the group consisting of urea, guanidine, alkyl substituted ureas, alkyl substituted guanidines, hydroxy methyl urea, and hydroxy ethyl urea, said alkyl groups containing 1 to 4 carbon atoms, said improvement comprising incorporating in said aqueous solution cadmium sulfate, the mol ratio of said compound producing an alkaline reaction when heated and said cadmium sulfate being from about 3 :1 to about 20:1, and the weight ratio of said compound producing an alkaline reaction when heated to said diazo compound being from 325:1, said metal sulfate forming a complex with said compound producing an alkaline reaction when heated.

6. A method as in claim 5 wherein the compound producing an alkaline reaction when heated is urea.

7. An improvement in a process for producing reproduction material wherein a base is coated with an aqueous solution of a coupling diazo compound, an azo coupling component, and a compound producing an alkaline reaction when heated, said compound being selected from the group consisting of urea, guanidine, alkyl substituted ureas, alkyl substituted guanidines, hydroxy methyl urea, and hydroxy ethyl urea, said alkyl groups containing 1 to 4 carbon atoms, said improvement comprising incorporating in said aqueous solution zinc sulfate, the mol ratio of said compound producing an alkaline reaction when heated and said zinc sulfate being from about 3:1 to about 20:1, and the weight ratio of said compound producing an alkaline reaction when heated to said diazo compound being from 3-25: 1, said metal sulfate forming a complex with said compound producing an alkaline reaction when heated.

8. A method as in claim 7 wherein the compound producing an alkaline reaction when heated is urea.

9. A process for reproducing an original which comprises: placing the original to be reproduced in superimposed relationship with a supported layer of a heat-sensitive composition, said composition comprising a mixture of a coupling diazo compound, an azo coupling component, a complex of a metal sulfate selected from the group consisting of cadmium sulfate, zinc sulfate, nickel sulfate, cobalt sulfate, aluminum sulfate, magnesium sulfate, and ceric ammonium sulfate, and a compound producing an alkaline reaction when heated, said compound being selected from the group consisting of urea, guanidine, alkyl substituted ureas, alkyl substituted guanidines, hydroxy methyl urea, and hydroxy ethyl urea, said alkyl groups containing 1 to 4 carbon atoms, the mol ratio of said compound producing an alkaline reaction when heated to said metal sulfate being from about 3:1 to about 20: 1, and the weight ratio of said compound producing an alkaline reaction when heated to said diazo compound being from 3-25 :1; irradiating said superimposed original with ultraviolet light to render the diazo compound incapable of coupling in the areas not protected by said original; and thereafter heating said supported layer of said heat-sensitive composition to a temperature of between about C. and 220 C. whereby a coupling reaction takes place and said original is visibly reproduced.

10. A process as in claim 9 wherein said sulfate is cadmium sulfate and wherein said compound producing an alkaline reaction when heated is urea.

11. A process as in claim 9 wherein said sulfate is zinc sulfate and wherein said compound producing an alkaline reaction when heated is urea.

12. A process for reproducing an original which comprises: placing the original having heat absorbing characters in sandwich relationship with a supported layer of a visibly heat-sensitive composition, said composition comprising a mixture of a coupling diazo compound, an azo coupling component, a complex of a metal sulfate selected from the group consisting of cadmium sulfate, zinc sulfate, nickel sulfate, cobalt sulfate, aluminum sulfate, magnesium sulfate, and ceric ammonium sulfate, and a compound producing an alkaline reaction when heated, said compound being selected from the group consisting of urea, guanidine, alkyl substituted ureas, alkyl substituted guanidines, hydroxy methyl urea, and hydroxy ethyl urea, said alkyl groups containing 1 to 4 carbon atoms, the mol ratio of said compound producing an alkaline reaction when heated to said metal sulfate being from about 3 :1 to about 20:1, and the weight ratio of said compound producing an alkaline reaction when heated to said diazo compound being from 325:1; irradiating said sandwich with heat producing radiations to efiect a coupling between said diazo compound and said coupler in the areas of said supported layer registering with the heat absorbing areas of said original, whereby said original is visibly reproduced.

13. A process as in claim 12 wherein said sulfate is cadmium sulfate and wherein said compound producing an alkaline reaction when heated is urea.

14. A process as in claim 12 wherein said sulfate is zinc sulfate and wherein said compound producing an alkaline reaction when heated is urea.

References Cited by the Examiner UNITED STATES PATENTS 2,653,091 9/1953 Greig 9675 2,709,655 5/1955 Frederick 9675 2,727,820 12/1955 Botkin 96-91 XR 2,732,299 1/ 1956 Morrison 96-49 2,756,144 7/1956 Ravich 96-49 2,995,466 8/1961 Sorensen 1173 6.8 3,076,707 2/ 1963 Lawton 117-36.8

FOREIGN PATENTS 1,249,913 11/ 1960 France.

OTHER REFERENCES Kosar: Photographic Sci. and Eng, vol. 5, No. 4, July-August 1961; pp. 239 and 243.

WILLIAM D. MARTIN, Primary Examiner.

RICHARD D. NEVIUS, MURRAY KATZ, Examiners. 

1. REPRODUCTION MATERIAL WHICH COMPRISES A SUPPORTED LAYER OF A VISIBLY HEAT-SENSITIVE COMPOSITION, SAID COMPOSITION COMPRISING A MIXTURE OF A COUPLING DIAZO COMPOUND, AN AZO COUPLING COMPONENT, A COMPLEX OF CADMIUM SULFATE AND A COMPOUND PRODUCING KAN ALKALINE REACTION WHEN EHATED, SAID COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF UREA, GUANIDINE, ALKYL SUBSTITUTED UREAS, ALKYL SUBSTITUTED GUANIDINES, HYDROXY METHYL UREA, AND HYDROXY ETHYL UREA, SAID ALKYL GROUPS CONTAINING 1 TO 4 CARBON ATOMS, THE MOL RATION OF SAID COMPOUND PRODUCING AN ALKALINE REACTION WHEN HEATED TO SAID CADMIUM SULFATE BEING FROM ABOUT 3:1 TO ABOUT 20:1, AND THE WEIGHT RATIO OF SAID COMPOUND PRODUCING AN ALKALINE REACTION WHEN HEATED TO SAID DIAZO COMPOUND BEING FROM 3-25:1. 